The material used for the propellers was also found to be weaker than expected, developing fatigue cracks after only a few years of use.
This is essentially a notch in the material which can be a potential source of fatigue cracks.
The damage was not enough to cause an immediate failure; a fatigue crack developed and got worse with each flight.
It began changing wheels before fatigue cracks could develop, much earlier than was legally required by the specification.
After the accident, 49 found bolts were investigated: 41 had fatigue cracks.
It had fatigue cracks and would have failed at some point.
Their plans became more urgent when fatigue cracks were discovered in the elevation drive system in September 1967.
When they showed fatigue cracks three of the bells were temporarily stopped.
After the accident 49 recovered bolts were investigated from which 41 had fatigue cracks.
Rogers said, "They had fatigue cracks in the fan blades!"
